1. Field of the Invention
The present invention relates to a heating device having a positive temperature coefficient (PTC) resistor plate as the heating element and having current supply electrodes and at least one insulating body, the individual portions of the device being held together by pressure.
2. Description of the Prior Art
A heating device having an optimized heating element consisting of PTC resistor material is known in the art, particularly from the German published application No. 27 43 880, corresponding to U.S. Pat. No. 4,177,375. The PTC resistor heating element, as essential features, has a thickness of only 0.5-2 mm given a specific electrical resistance of the PTC resistor material kept within a relatively narrow range, the PTC resistor material having, in addition, a Curie temperature which is at least 50.degree. higher than the shutdown temperature provided for the heating device.
Particularly in the German published applications P No. 28 06 159, corresponding to U.S. Pat. No. 4,230,935 and P No. 28 16 076, corresponding to U.S. Pat. No. 4,223,208, measures for installing such a PTC resistor heating device are set forth in which the PTC resistor plate is held under pressure between the heat-dissipating plates.
In all previous instances, current supply electrodes have been provided for the current supply into the PTC resistor plate on the PTC resistor material itself. Surface metalizations of aluminum, of In-Ga-Ag multiple layers and, recently, also of enameling silver have been employed.
Wide areas of employment for heating devices having PTC resistor plates have been opened up. For the practical introduction of such heating devices, the decisive matter is the technical expense which is reflected in the price and which, for mass production, of course, is to be held to a minimum.